FRANKFURT, West Germany (AP) _ Prosecutors on Wednesday announced criminal probes of a key company in the Libyan chemical weapons plant dispute and a Bavarian company that reportedly delivered sophisticated equipment to Libya's air force.

The new probes bring to three the number of criminal investigations in the widening scandal, and in each case authorities acknowledged they were checking allegations made by West German news reports.

Since the first allegations of West German involvement were published early this month, the nation's news media have been particularly aggressive about pursuing the story.

Politicians, meanwhile, have had to retract their earlier denials of West German involvement with the plant in Rabta, 60 miles south of the Libyan capital of Tripoli. Washington says it was built to make chemical arms, while the Libyan government of Col. Moammar Gadhafi says it will make pharmaceuticals.

In Bonn on Wednesday, Chancellor Helmut Kohl sat with other lawmakers as his chief aide, Wolfgang Schaeuble, addressed an acrimonious session of Parliament about when the government in Bonn first learned of the charges.

Schaeuble said the U.S. government in May passed on tips about West German involvement in the suspected Libyan chemical weapons plant. He said the tips also involved the alleged German help in providing Gadhafi's air force with midair refueling capability.

The Frankfurt prosecutor's office said Wednesday it has opened a criminal investigation of the now-defunct I.B.I. Engineering company, which U.S. officials have accused of providing equipment for the plant.

''Our authorities opened the probe against I.B.I. on Friday because of suspicion of reported violations of export laws,'' Frankfurt prosecutor Jochen Schroers told The Associated Press in a telephone interview.

He declined to provide further information about I.B.I., which allegedly provided the contracts to the West German companies to build the plant.

West Germany's ARD television network reported that about 50 companies just in the greater Frankfurt area are suspected of having taken part. Federal customs officials are also investigating.

In Munich, chief prosecutor Heinz Stocker said he was looking into a report in this week's Der Spiegel magazine that says the Intec Technical Trade and Logistik company has been helping Libya develop the ability to refuel its warplanes while in flight.

The prosecutor said he had already planned to investigate Intec, but added authorities want to know whether the report in Spiegel is correct.

''That is a point of the investigation,'' Stocker told the AP in a telephone interview late Wednesday afternoon. ''We will have to see what comes out.''

The probe against Intec ''concerns fuel tank equipment sent to Libya'' and may also involve violations of West Germany's export laws, he said. ''We don't know what was done with this equipment in Libya.''

Der Spiegel reported 10 Intec-hired engineers are playing a key role in helping Libya fit warplanes and transport planes with equipment necessary for mid-air refueling to extend the warplanes' range.

Intec is in the town of Vaterstetten near Munich.

Last week, Offenburg prosecutor Werner Botz announced he was investigating the Imhausen-Chemie company, which reportedly also had a major role in the construction of the suspected chemical weapons plant.

Offenburg is near the Black Forest town of Lahr, where Imhausen has its headquarters.