The border city of Tijuana is a flashpoint for Mexico's drugs gangs
Mexican troops and police are closely guarding a Tijuana hospital to prevent reprisals against eight alleged members of a drug gang hurt in recent clashes.
Only emergency cases are being admitted to the hospital.
Fifteen people were killed in clashes on Saturday between members of rival gangs in the city, near the US border.
About 900 people have been killed in drug-related violence in Mexico this year. The government has sent thousands of troops to fight the drug cartels.
Nearly 200 people have been killed in Tijuana alone this year.
Authorities have despatched more than 3,000 soldiers and federal police to Tijuana after Saturday's clashes, to join the several thousand already deployed by President Felipe Calderon.
Soldiers carrying machine guns have sealed off the hospital to all but emergency cases and a severely restricted number of visitors.
Since taking office in late 2006, President Calderon has sent nearly 30,000 soldiers and federal police to fight Mexico's powerful drugs cartels.
Despite the extra security, the drug-related violence has continued as gangs struggle to control lucrative trafficking routes.
Police said the 15 people killed in Saturday's gun battles were all from the Arellano Felix cartel, which has come under pressure from a rival gang.
The cartel rose to prominence in Tijuana in the 1980s. Much of its activities centre on smuggling Colombian cocaine through Mexico to California.
Police say the gang has been weakened by the arrest or killing of many of its top leaders in police raids.
It has also come under pressure from a rival gang from the west coast state of Sinaloa, led by Mexico's most wanted criminal, Joaquin "Shorty" Guzman.