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An armed man who held dozens of people hostage on a public bus Tuesday was shot dead by police in Rio de Janeiro.

The man had been threatening to set the vehicle on fire, Brazilian police said.

Earlier, the Federal Highway Police said negotiations were underway with the man who had been holding 37 people hostage since about 5:30 a.m. on a busy bridge linking the suburb of Sao Gonçalo to downtown Rio de Janeiro.

At least six hostages were released before the man was shot.

Authorities said the man had spilled gasoline in the bus and threatened to set it on fire. 

The man did not make any particular demands and appeared to to have "psychological problems," a spokesperson for the traffic police said on TV Globo.

Snipers and police surrounded the bus and blocked traffic, with hundreds of vehicles waiting in line as the drama unfolded.

Sao Gonçalo is a violent, impoverished suburb separated from Rio by Guanabara Bay.