An attempt to honour a dead baseball fan's last wish went horribly wrong on Friday, forcing the evacuation of Safeco Field, the home of the Seattle Mariners baseball team, amid fears of a bio-terror attack.

A small private plane swooped low over the stadium shortly after 1000 (1700 GMT) and was seen dropping a package, which exploded on impact spraying the area with a mystery white powder.

In light of 9-11 and the fact that this involved an aircraft, we were very concerned that this might be some kind of attack

Harold Webb, Seattle Fire Department

Officials feared a terrorist attack, and evacuated the stadium and nearby streets and offices.

But in reality the package contained the ashes of a devout Mariners fan who had wanted his remains cast over the field.

Unfortunately, the bag did not open high in the air as planned, but hit the ground intact.

Attack jitters

In the wake of 11 September Americans are on a state of heightened alert - constantly on the lookout for possible terrorist threat.

Earlier in the day, the FBI had warned that terrorists might try to use small aircraft for suicide attacks.

The team are considering legal action

In the Seattle alert, airspace was cleared, city streets were closed and an entire neighbourhood cordoned off.

"In light of 9-11 and the fact that this involved an aircraft, we were very concerned that this might be some kind of attack," Seattle Fire Department spokesman Harold Webb said.

A hazardous materials team was despatched to investigate and the small plane tracked to a nearby airfield.

Wife's request

When the pilot was quizzed he explained that what he had actually dropped were cremated human remains.

"The guy (who died) was apparently a real Mariners fan and wanted his ashes over the field," Dave Menzimer, chief pilot of Wings Aloft, the company that owns the plane, said.

He described the flight as a "routine ash drop" carried out at the request of the deceased man's wife.

There is a precedent for a small plane attack

But officials at the Mariners were not best pleased with this tribute to their team.

A spokesman said the club was considering seeking charges against the airplane operator.

"We did not know this was happening and we're quite upset about it. This could have been a very serious situation," Tim Hevly said.

Flight rules prohibit dumping any object from an airplane, and the release of cremated ashes over an urban area.

The US Federal Aviation Administration is investigating the incident.

"This was a quite reputable local company that does this a couple of times a year, but honestly, I've never heard of a location such as this," Mr Kenitzer said.