LOS ALAMOS, N.M. — The Latest on US efforts to ramp up nuclear pit production (all times local):

4:50 p.m.

The agency that oversees the nation’s nuclear weapons stockpile says further study is needed to determine the best option for the United States as it looks to ramp up production of the plutonium cores that trigger nuclear weapons.

The National Nuclear Security Administration said Monday that a team of external and internal engineering experts will further analyze the two options that were identified as part of an earlier review that looked at the most efficient and cost effective means of making the pits.

Agency spokeswoman Lindsey Geisler tells The Associated Press the options include leaving the work to Los Alamos National Laboratory or moving it to the U.S. Energy Department’s Savannah River Site in South Carolina.

It’s not clear how long the extra analysis will take, but the agency said new pits must be made to ensure the nation’s nuclear forces are flexible and tailored to deter 21st-century threats.

2:28 p.m.

The agency that oversees the nation’s nuclear weapons stockpile has yet to release a report on the risks and capabilities of Los Alamos National Laboratory and other U.S. Energy Department sites when it comes to producing plutonium cores for the weapons.

The report by the National Nuclear Security Administration was due over the summer but nothing has been made public other than a redacted summary sheet obtained by a watchdog group in the wake of recent congressional briefings.

The summary suggests it would be most costly to continue producing plutonium pits at Los Alamos.

Members of New Mexico’s congressional delegation suggest the evaluation process was flawed. Others are voicing concerns about Los Alamos’ safety record.

No new pits have been made since 2011. The Energy Department wants to ramp up production to 80 pits annually by 2030.