BONN, JUNE 27 -- A West German businessman who helped Libya build a chemical weapons plant was sentenced today to a five-year prison term, and government sources said they are investigating two more companies suspected of helping the Libyans build another suspected poison gas facility.

Bonn sources said West Germany has received reconnaissance photographs taken by the U.S. Central Intelligence Agency showing construction of an underground facility at Sebha, about 60 miles from the plant Juergen Hippenstiel-Imhausen helped build at Rabta. U.S. intelligence agencies believe that Libyan leader Moammar Gadhafi staged a fire at the Rabta site in March.

The sources said the photographs indicate that Libya is constructing a secret, high-technology facility that could be a poison gas factory.

Government sources said the two companies, Rose of Stuttgart and Abacus in Ulm, are suspected of sending Libya materials that closely follow the plans the firm of Imhausen-Chemie developed for the original Libyan plant.

Prosecutors learned about the alleged involvement of Abacus when a manager at Siemens, the West German computer conglomerate, told officials that Abacus had ordered a central computer processing unit identical to one used at the Rabta plant.

Spokesmen for both Abacus and Rose today refused to comment on the allegations.

Prosecutors also said they have launched new investigations into West German businessmen, an Iraqi middleman and a Belgian transport company suspected of helping the Libyans on the Rabta plant.

The sentence given Hippenstiel-Imhausen in a Mannheim court was 18 months less than that demanded by a prosecutor who called the chemical executive "the supreme salesman of death." Some opposition legislators immediately denounced the sentence as too light.

Most of the sentence handed down to Hippenstiel-Imhausen stemmed from his conviction for evading about $9.5 million in taxes on his profits from the Libyan deal rather than for his violation of West Germany's recently toughened law against the export of chemical and biological weapons.

Judge Juergen Henninger told Hippenstiel-Imhausen that he "knowingly delivered to Libya an installation suitable for the production of poison gas weapons" and accused the executive of covering up his company's involvement.

Henninger said Hippenstiel-Imhausen's activity caused "deep damage" to West Germany's relations with its allies, who accused Bonn of tolerating corporate cooperation with the Libyans. But the judge said a criminal court is "not the place for a moral judgment of the accused" or a parliamentary investigation, and he refused the prosecution's entreaties for the maximum sentence.

"The punishment is much too light," said Albrecht Mueller, a Social Democratic legislator who has pushed for tighter export controls than those imposed by Chancellor Helmut Kohl last year. "You can export a chemical weapons factory to Libya and you get three years maximum, but you can get five years for a tax violation. This doesn't make sense."

Mueller said Hippenstiel-Imhausen will likely serve three years of his term and emerge from prison "rich from the millions he got from Libya."

Mueller pledged to seek new legislation that would confiscate profits made from illegal exports. "All industrial nations have a responsibility on this, but we Germans have a special responsibility," he said. "A people with a history with poison gas like ours must never again have anything to do with these things."

A government spokesman defended the West German law, calling it the tightest in the world. The law allows prosecution for export of expertise as well as materials and gives the government the right to examine projects that West German companies undertake in other countries.

Hippenstiel-Imhausen pleaded guilty to charges that he secretly sold the $150 million Rabta plant to Libya, which claims the factory made only medicines. Prosecutors said the plant was designed to make two kinds of nerve gas, but Hippenstiel-Imhausen admitted only that the plant was intended as a "multi-purpose chemical" facility.

Hippenstiel-Imhausen, who said he made a $12 million profit on the deal, said he worked with a Libyan partner to use a Hong Kong company as a cover for the illegal export. Materials were marked for export to Hong Kong; after arriving there, they were immediately sent to Libya, Hippenstiel-Imhausen said.