Prosecutors raided a dentist group's office in Tokyo on Thursday, amid allegations it exceeded political donation limits in its support of Liberal Democratic Party lawmaker Midori Ishii.

A special investigative arm of the Tokyo District Public Prosecutor's Office searched the office of the Japan Dental Federation, a political body linked to the country's dental association, on suspicion of violating the Political Funds Control Law.

While the federation directly offered ¥45 million to Ishii's support group in 2013, it is alleged to have also provided ¥50 million to the group the same year through the support group of another lawmaker, according to sources familiar with the matter.

The law allows a political group to donate up to ¥50 million a year to another political group.

The two support groups are both headed by Mikimasa Takagi, president of the Japan Dentist Federation, and their offices are housed in the same building as the federation.

Ishii is a dentist and a one-time senior official of the Japan Dental Association, which represents the nation's roughly 65,000 dentists.

Backed by the group, she was elected to her second six-year term as a House of Councilors member in July 2013.