"We are committed to conducting a thorough and comprehensive investigation as quickly as possible, and we continue to put the safety of our customers and employees first," said Muni Executive Director Nathaniel Ford in a statement issued early this afternoon.
Investigators were also still surveying the extent of the damage to the two light-rail vehicles, Muni reported.
An update on the investigation is expected by the end of the week. According to Muni and the San Francisco Fire Department, 16 people were injured by the mid-afternoon crash, and 12, including the two Muni drivers, were hospitalized.
According to San Francisco Fire Department spokeswoman Mindy Talmadge, the various injuries ranged from minor to potentially life threatening.
Four of the injured were reportedly released from San Francisco General Hospital the same day, Muni reported.
"Our thoughts continue to be with the individuals who were injured on Saturday," Ford said.
The crash occurred at about 2 p.m. at Fourth and King streets, one block south of AT&T Park.
According to Muni, a one-car T-Third train going westbound on King Street between Third and Fourth Streets struck a two-car N-Judah train that was stopped at the Fourth Street traffic signal.
The incident caused light rail service in the area to be suspended for about two-and-a-half hours and shuttle service was used to transport passengers.
The T-Third train operator has been a light-rail operator since 2004; the N-Judah operator since 2007, Muni reported.