BERLIN – German prosecutors are investigating about 100 professors across the country on suspicion they took bribes to help students get their doctoral degrees, authorities said Saturday.

The investigation is focused on the Institute for Scientific Consulting, based in Bergisch Gladbach, just east of Cologne, which allegedly acted as the intermediary between students and the professors, said Cologne prosecutor's spokesman Guenther Feld.

Feld confirmed reports of the investigation in both Focus magazine and the Neue Westfaelische newspaper, but would not give further details.

The Institute for Scientific Consulting did not answer its phone Saturday.

According to the two publications, students paid between euro4,000 to euro20,000 ($5,700 to $28,500) to the company, which promised to help them get their doctorate degrees through its extensive contacts within university faculties.

The Neue Westfaelische newspaper reported that "hundreds" of students were involved, and that the company paid professors between euro2,000 to euro5,000 when their clients had successfully received their Ph.D.'s. It was not clear whether the students knew that bribes were being paid.

The professors are being investigated on suspicion of fraud, Feld said.

"The supervision of a Ph.D. thesis is a public service, and one is not allowed to take money for it," Feld told the newspaper.

So far, evidence points to the involvement of about 100 professors across the country spanning "numerous disciplines," Feld was quoted as saying. Most are people teaching classes on a contract basis, rather than full-time professors, he said.

Focus reported that the investigation involved universities in Frankfurt, Tuebingen, Leipzig, Rostock, Jena, Bayreuth, Ingolstadt, Hamburg, Hannover, Bielefeld, Hagen, Cologne and Berlin.

The investigation was opened last year after another probe of the Institute for Scientific Consulting in connection with a similar scheme.

After authorities searched the firm's headquarters in March 2008, the company's head was charged with paying bribes in a case involving a Hannover University law professor. The man, whose name was not released in line with German privacy laws, was found guilty and sentenced in July 2008 to 3 1/2 years in prison, and fined euro75,000.

The professor, whose name was also not released, was found guilty as well and sentenced to three years in prison for accepting the bribes.

The professor confessed in court to accepting nearly euro200,000 to serve as a faculty adviser to more than 60 doctorate students between 1998 and 2005.

The professor said he needed the money to renovate his Hamburg mansion.

Corruption everywhere.