The federal government sued two companies in order to recover at least $6.5 million spent so far in cleanup costs at the Halby Chemical superfund site near the Port of Wilmington.

The U.S. Attorney General filed suit in District Court in Wilmington, seeking past and future cleanup costs from Witco Corp., the successor by merger to Halby Chemical Co., and the Pyrites Co., a unit of U.S. Borax Inc.