The Interior Ministry has ordered the police to widen the scope of a check of Moscow's markets that has already seen nearly 500 people detained.
The operation started Monday, two days after a police officer was badly beaten attempting to detain a rape suspect at the Matveyevsky Market.
Police have been tasked with catching everybody who participated in the attack on the officer, Anton Kudryashov, as well as checking the migration documents and trading licenses of the city's merchants in markets and other types of trading outlets.
Interior Minister Vladimir Kolokoltsev initially gave the police just two days to complete their checks, Izvestia reported Tuesday.
But the ministry has since said that the police will be given more time to complete their work, while a parallel investigation into the police checks is also under way, Interfax reported.
The police chief of the district where the incident took place was fired Monday, and investigators are looking into the actions of the beaten officer, Kommerant reported Tuesday.
Video evidence being used in the investigation shows Kudryashov's fellow officers failing to intervene while he was being attacked, or to detain his assailants afterward, the report said.
A crowd of 20 to 25 people attacked the police officers.
Kudryashov is set to undergo surgery, and police said he would probably need to have a metal plate put in his skull.
Police detained one suspected attacker, Magomed Rasulov on Monday while he was trying to flee the city on a bus.
A criminal case has been opened on charges of making an attempt on the life of a police officer. The charge carries a maximum punishment of life in prison.