Every show - across the board - has suffered - and we were just not able to hold on to see what would happen

Jordan Roth, Producer The Rocky Horror Show

"We may be going through a period in which even people who are not afraid and certainly willing to do different things may not feel like going to a Broadway play.

"We want to make sure they get through this period of time.

"If they need help - loans, other financial assistance - to get through this period because things are going to be obviously different two, three, four weeks from now and we want to get them through this period."

The shows are waiting for union agreement to make their closure official at such short notice.

The Rocky Horror Show's producer Jordan Roth explained that the drop in audiences was widespread.

"Every show - across the board - has suffered and we were just not able to hold on to see what would happen."

The American entertainment industry effectively shut down in the immediate wake of Tuesday's attacks.

Security checks around Broadway make a visit tense

It was both a mark of respect for the victims of the disaster and a reflection of the mood of a nation too shocked to consider having a good time.

However, though all 23 shows on Broadway reopened for business on Thursday, much of the public stayed away.

This, added to the estimated $3m (�2.04m) lost by show producers during the shutdown, has made continuation untenable for some productions, especially the least successful.

Sombre

The Rocky Horror Show, which opened in November, had been struggling before the suicide attacks.

The Irish comedy Stones in His Pockets was not doing as well as hoped, despite being a big hit in London's West End.

If You Ever Leave Me, I'm Going With You, a comedy written by and starring Renee Taylor and Joe Bologna, was also a weak performer.

Yet, it is not just the less popular productions that are being affected by the sombre mood of the public and by visitors staying away.

Even the Tony Award-winning smash The Producers, starring Matthew Broderick, reported a marked drop in ticket sales, according to trade magazine Variety.

Cancellations for The Producers in the last few days stand at around 150 per performance, according to Variety.

Other long-running favourites - particularly among tourists - such as Les Miserables and The Phantom of the Opera also saw a drop in audiences.

A usually busy Times Square showed the effect of the attacks

And for the first time in four years, musical The Lion King did not sell out. And the future of other big musicals such as The Music Man and Kiss Me, Kate could now be in doubt.

Wages

Many show producers seem to believe it will take a long time for the lucrative tourist business to return.

Emanuel Azenberg, a producer of Stones in his Pockets commented: "New York is the mecca for the theatre, and the city was threatened in a huge way.

"It is quite conceivable we could do less business this week than we did last week.

"At least for three or four days, people who were stuck in New York could go to the theatre. Now those people have left town."

Union representatives are due to decide in the next couple of days whether to allow shows to close without giving a week's notice.

They are also said by Variety to be considering other cost-saving measures such as a 30% reduction in salary for theatre staff.