огородить(to stop people from getting into an area by surrounding it with police, soldiers, etc. OALD. Police cordoned off part of the city centre... The police cordoned everything off. CoCoB Alexander Demidov)
перекрыть(дороги, улицы, центр города и т.д.: On Monday, police cordoned off entry points to determine if drivers had a valid reason to be in Moscow, according to state media and witnesses.Халеев)
оградить место преступления(After the victim was taken away by authorities, the police had to cordon off the crime scene with police tape until the forensics team arrived at 10pm.4uzhoj)