BUFFALO, N.Y. (AP) _ New York state should help pay for cleaning up the Love Canal chemical dump because it owned part of it and dug up tons of toxic waste there, a lawyer said Tuesday in closing arguments of a liability lawsuit.

Thomas Truitt, an attorney for Occidental Chemical Corp., said the federal Superfund law applies to the state because it was a part-owner of the notorious Niagara Falls site.

The dump was created by Hooker Chemicals & Plastics Corp. in the 1940s and 1950s. Occidental bought Hooker in 1968. The site became a by-word for the nation's toxic waste problems in the 1970s when chemicals leaked into houses built on the site, forcing thousands to flee.

The state acquired a small strip of the site in 1968 to build a highway and sewer.

During that construction, the state excavated ''at least 1,000 cubic yards of chemical waste, piled it onto an adjacent property where it remained unfenced for several weeks, and then transported it in leaking dump trucks off site,'' Truitt said.

State officials were aware that toxic chemicals were buried there, Truitt said.

Eugene Martin-Leff, the state's lead attorney, said the construction did not disturb the wastes.

''Occidental, which has been held fully responsible for Love Canal, seeks a companion today to share the blame for much of the contamination at the site,'' Martin-Leff said.

New York is suing Occidental for about $150 million in cleanup costs, $250 million in punitive damages and about $265 million in other expenses. U.S. District Judge John T. Curtin has already ruled Occidental liable for at least part of that cost.

Occidental countersued the federal, state and Niagara Falls governments and the city school board, claiming each is also liable. Tuesday's arguments concerned only Occidental's claim against the state.

Curtin is expected to take several months to decide whether any of the governmental bodies are liable. A separate trial would then be held to determine how much each should pay.