Gunmen who held Philippine children and teachers for over nine hours in a bus had dud grenades and authorities are investigating whether the hostage crisis was a political gimmick, officials said yesterday.

Two men armed with grenades, an Uzi submachine gun and a revolver held 26 children and three teachers from a day care centre in a bus parked outside Manila City Hall on Wednesday, drawing a blaze of publicity. A radio station quoted officials at the local police Explosives and Ordnance Division as saying the grenades were real but had no detonating mechanism. There was no immediate word on the other weapons used in the hostage-taking.

?From the very start we looked at the possibility of political motivation,? Manila Mayor Jose Atienza told the radio station. ?The campaign season is peaking. This could be part of a political exercise of some people, and we discussed the matter.?

One of the gunmen, Jun Ducat, contested elections to the House of Representatives in 2001, but was unsuccessful. Congressional elections this year are to be held in May.

?Was Ducat acting alone or is a political figure behind him? We have to look at that angle also,? Atienza said.

The hostages were later released unharmed and the children were sent home after checks at hospital.