Medical laboratories are coming under growing suspicion as the sources of the debris, including used syringes, that have been polluting beaches in the New York City area, the city's sanitation chief says.

Environmental Conservation Commissioner Thomas Jorling emphasized Thursday that the state probe had not yet turned up enough evidence to "sustain the burden of prosecution."But New York City Sanitation Commissioner Brendan Sexton, whose department also is investigating the pollution, as is the federal government, said his agents are closing in on between two and eight medical labs believed to have illegally dumped wastes along the coast.