By Brian Rowan BBC Northern Ireland chief security correspondent

In the Northern Ireland peace process it seems that crisis is always lurking just around the corner, and this is another of those times when there is a nervousness about the future.

The ceasefires have not meant the paramilitary organisations have gone away, and the security world, along with politicians and governments, are once again looking closely at what they have been up to.

The security assessment suggests that the IRA's activities in Colombia were cleared by people at the top of the organisation

With guns and bombs being used on the streets of Belfast, the main loyalist organisations and the IRA have been accused of involvement.

Two other incidents in the past year have also meant that the IRA has remained under a constant security spotlight.

Despite denials, sources continue to link the organisation to the theft of Special Branch documents from Belfast's police headquarters at Castlereagh.

IRA denial

And the arrest of three republicans in Colombia in August last year has raised the question: What was the IRA up to?

James Monaghan, Martin McCauley and Niall Connolly now face trial on charges of training left-wing FARC guerrillas and travelling on false passports.

On Thursday, the IRA repeated its denial that it had any "military" involvement in Colombia.

A spokesman said the IRA firmly rejected "unsubstantiated allegations about IRA activity in Colombia" which he said were being made by unnamed securocrats who had consistantly sought to undermine the peace process".

But a security assessment given to the BBC suggests something entirely different.

"PIRA (Provisional IRA) have been using Colombia as a training ground to carry out tests with their engineering department as they are no longer able to use the Irish Republic due to the current political climate," the assessment reads.

It continues: "It also allowed them free-range to explore the new prototype of devices which they were developing at that time."

Rockets

"At that time", means prior to the arrests of Monaghan, McCauley and Connolly.

The security assessment given to the BBC suggests the new weapons which were being developed included rockets, and that the IRA's activities in Colombia were cleared by people at the top of the organisation.

Our sources say it was "definitely sanctioned at army council level" by the organisation's chief of staff Thomas 'Slab' Murphy and by Brian Keenan, who represents the group in talks with the international weapons decommissioning body.

So what's in this for the IRA?

According to security sources, it's "retaining the ability to manufacture new technology without the danger of being arrested, and keeping the engineering department intact and able to function if and when required if there is any change in the way ahead".

David Trimble: Allegations will cause difficulty

Unionists are alarmed. They view the suggestion the IRA was developing new weaponry as a clear breach of their ceasefire.

One of David Trimble's unionist colleagues in the Northern Ireland Executive, Michael McGimpsey, demanded answers from the republican leadership and from the British Government.

In response to questions from the BBC, security sources say the relationship between republicans and the FARC was "developed over a number of years, probably brokered through Cuban involvement and definitely developed on the PIRA side by Brian Keenan and Evelyn Glenholmes".

'Most wanted'

Hers is a name from the distant past. She was once labelled "Britain's most wanted woman" but, in the mid-1980s, extradition proceedings against her in the Irish Republic failed because of problems with the warrants.

Scotland Yard had wanted to question her about a series of bombings in Britain in 1981 but, after being freed by a Dublin court five years later, she disappeared.

The IRA has tried to fight off claims about Castlereagh and Colombia but has not managed to do so

Evelyn Glenholmes was on the run, and security sources believe the fluent Spanish speaker spent five years in Cuba.

Now she is back living in Belfast.

Two years ago, the Northern Ireland Office responded to a request for information.

They checked with the prosecuting authorities and confirmed she was no longer wanted.

Some years earlier, the Crown Prosecution Service had reviewed her case and concluded "there was no longer sufficient evidence to afford a realistic prospect of conviction".

But this information was not made public at the time.

'On the run' cases settled

In response to a question from the BBC on Glenholmes, a spokesman at the Northern Ireland Office said: "Decisions on the prosecution of individuals are a matter for the prosecuting authorities which are independent of government."

It is not clear if Evelyn Glenholmes was one of the cases raised by Sinn Fein in their discussions with the British Government about people "on the run".

But I have been told that "quite a few" cases have now been settled with another source suggesting the figure runs to "some dozens".

All of this emerging at this time, will undoubtedly cause difficulties for David Trimble and his party - and some fear that another crisis is not that far away.

The IRA has tried to fight off claims about Castlereagh and Colombia but has not managed to do so.

And the problem for the republican leadership is that unionists are more inclined to believe what security sources have been saying.

The peace process is once again skating on thin ice.