Abandoned barrels of unknown substances found near a wildlife refuge in East Palo Alto shut down part of Bay Road Monday afternoon.

The barrels, at 2191 Bay Road, near the Baylands Nature Preserve, were discovered by a water district ranger on patrol, according to Menlo Park Fire Protection District Captain Scott Mariani.

The department blocked off the end of Bay Road leading out to the bay beginning at 1:30 p.m., delaying several trucks on their way to industrial facilities.

A hazardous-materials team and San Mateo County environmental health team were investigating the site.

"There's a whole pile at the end of the road," Menlo Park Fire Protection District Chief Harold Schapelhouman said.

He described the find as two 55-gallon drums, one full and the other empty; one 20-gallon drum; between 15 and 20 five-gallon drums; and numerous five- and one-gallon drums and one-quart paint containers.

Laboratory tests will determine what's inside the containers, he added.

City workers who went out to retrieve the drums, which were initially thought to be debris, found some containers were not empty but reported feeling no ill effects, Schapelhouman said.

Mariani said the ends of Bay Road and Weeks Street are popular spots for illegal dumping. Violators back in at night to abandon a wide range of materials "and split."

The incident has caused truck traffic going to Romic Environmental Technologies, a hazardous-materials recycling company, to back up along the roadway, but the barrels do not appear to be associated with the waste disposal company, Division Fire Chief Frank Fraone said.