A jury will resume deliberations Monday in a criminal air pollution case that accuses Citgo Petroleum Corp. of knowingly breaking federal air quality laws at its Corpus Christi refinery.

Lawyers presented final arguments on Friday after a grueling and technical trial that began May 18. Jurors deliberated Friday afternoon, then went home for the weekend.

The case specifically involves allegations that open-air storage tanks at Citgo's East Plant refinery emitted illegal amounts of benzene, which research has linked to cancer. More broadly, however, the case tests criminal enforcement of the Clean Air Act.

Although other criminal indictments under the act have resulted in guilty pleas, the Citgo case is the first to go to trial alleging emissions violations, prosecutors said.

"The question is whether companies like Citgo, who blatantly violate the law over a period of time, will be held accountable," said Justice Department lawyer Howard Stewart, lead prosecutor in the case.