LIMA (Reuters) - An ombudsman on Thursday called for prosecutors to investigate Peruvian builder Grana y Montero and other partners of Brazil’s construction conglomerate Odebrecht in a corruption probe that has already sunk Grana’s shares.

Grana, Peru’s biggest engineering conglomerate and Odebrecht’s most important partner in Peru, has repeatedly denied having known about $29 million in bribes that Odebrecht has said it distributed in Peru from 2005 to 2014.

But ombudsman Walter Gutierrez, whose office defends the interests of the public, said Grana cannot be taken at its word.

“If I’m your partner, I know about the financial status and relevant actions of the business...how could I not know, or at least have a suspicion” if bribes were paid? Gutierrez said at a press conference with foreign media. “They should be investigated.”

The comments added to growing calls from lawmakers for Grana to be included in an investigation into Odebrecht’s past kickback schemes after Odebrecht promised to provide prosecutors with relevant testimony and documents.

Grana said it was not under investigation but would cooperate fully if needed to help prosecutors with their work or to clear up doubts.

“We’ve instructed our lawyers to study this case deeply and determine next steps. We’ve asked that whatever we do that our willingness to collaborate with the state...be respected,” Grana said in a statement.

The value of Grana’s shares have dropped about 37 percent since Odebrecht signed a settlement with U.S. prosecutors that made public bribes that Odebrecht admitted to distributing across Latin America.

Grana was Odebrecht’s junior partner on several projects that are now under investigation: two highway contracts awarded in 2005, a metro line it still operates and a natural gas pipeline contract that the government revoked last month after financing got snagged on corruption concerns.

Prosecutors have accused former president Alejandro Toledo of taking $20 million in bribes to help Odebrecht win the highway contracts. Toledo has not been convicted of any crimes and has denied wrongdoing. He is being sought by authorities.

Grana owns a minority stake in Odebrecht’s stalled irrigation project Chavimochic III, which the government wants Odebrecht to exit.. Odebrecht has said it was willing to sell off its remaining contracts with Peru amid calls from the government to leave.