There has been heavy fighting in northern Mexico between the security forces and members of the powerful Sinaloa drug cartel after one of the group’s leaders was discovered.
Ovidio Guzmán López was found during a routine patrol in Culiacán.
He is the son of drug lord Joaquin “El Chapo” Guzmán, who was sentenced in the US to life in prison plus 30 years.
Guzmán, 62, was found guilty in New York of 10 charges, including drug trafficking and money laundering.
He escaped a Mexican jail through a tunnel in 2015, but was later arrested. He was extradited to the United States in 2017.
Guzmán is a former head of the Sinaloa cartel, which officials say was the biggest supplier of drugs to the US.
What happened in Culiacán?
The state government said Ovidio Guzmán was found in a house by a police patrol on a routine search.
It said cartel members subsequently launched the huge attack in an attempt to seize him back from the authorities.
Ovidio Guzmán, said to be in his 20s, is believed to have played a key role in the Sinaloa cartel, following the arrest of his father.
He is wanted in the US on several drug-related charges, Mexican media report.
He was briefly detained before being released by the police.
There have been no official reports of fatalities, but pictures have emerged apparently showing dead bodies on the streets of the city.
The Sinaloa state government said it was “working to restore calm and order in the face of the high-impact incidents that have occurred in recent hours in various points around Culiacán”, AFP news agency reports.