An Iranian news website is reporting several suspects have been arrested over last week’s killing of an Iranian nuclear scientist.

Ali Larijani, speaker of the Iranian parliament, said the suspects are being interrogated, and the investigation is continuing.

Mostafa Ahmadi Roshan, an official in Iran’s nuclear enrichment facility in Natanz, was killed in an explosion Wednesday, January 11, after attackers attached a bomb to his car in Tehran.

Iran accused the U.S., Britain and Israel of involvement.

Washington denied any role in the assassination, and London condemned the killing of civilians. Israel has not commented publicly.

The West believes Iran is building nuclear weapons. Iran denies that, AP reported.