The prison killing of 14 gang members happened quietly throughout the day in what authorities called a "purge" within the gang known as 18th Street, and went unnoticed until it was time to close the inmates in their cells, security officials said Sunday.

All the dead were strangled, stabbed and were found in various locations of the prison, said Benito Lara, minister for justice and public security. Officials called a state of emergency inside the at the Quezaltepeque facility, 15 miles (25 kilometers) northwest of San Salvador and stopped all visits.

"Everything was done in a very quiet manner throughout the day," Lara said in a press conference. "Everything appeared normal, until we started to do our routine count of prisoners and started to notice that some had been killed."

Authorities said they didn't enter while the killings were going on because there are no video cameras monitoring the inside of the prison, which only has members of the 18th Steet gang, one of the two most powerful criminal organizations in El Salvador.

A mother of one of the prisoners was also killed hours before the slaying in the municipality of Aguilares north of the capital in what authorities believe was a related attack.

According to authorities, the gang members are involved in the majority of crimes committed in the country and are also 60 percent of crime victims.

The Revolutionaries, a faction of 18th Street, are blamed by the government for recent attacks on bus drivers who refused to honor the gang's demand that public transportation be suspended.