Sen. Elizabeth Warren (D-Mass.) (J. Scott Applewhite/AP)

Democratic senators want to know — in detail — how the government is trying to reunite migrant families separated after crossing the U.S.-Mexico border.

In a letter Monday, Sen. Elizabeth Warren (D-Mass.) and 10 colleagues asked federal officials for information that would reveal the progress of the reunification efforts. They asked for anonymized lists of all children and adults who were separated from family members at the border; how long they have been detained and where; and whether their family members have been successfully contacted.

“Since the President’s Executive Order was signed on June 20, 2018, the Administration has repeatedly indicated that families would be reunited,” the senators wrote to Health and Human Services Secretary Alex Azar and Homeland Security Secretary Kirstjen Nielsen.  “However, the hastily-signed order provided no clarity on how to reunify families, or how to handle families that have already been separated or new families that cross the border seeking asylum.”

The letter is the latest attempt by lawmakers to try to understand how HHS and DHS are managing the reunification effort. Democrats pressed Azar for answers last week when he testified on prescription drug prices before the Senate Finance Committee.

Roughly 2,500 migrant children were separated from their parents after Attorney General Jeff Sessions announced a “zero-tolerance” policy toward illegal border crossings in May. About 500 of them have been reunited with their parents.

The Trump administration must comply with two court decisions related to its policy: an injunction issued last week requiring the government to begin reuniting families and an older court settlement that requires immigration agencies to release minors in their custody after 20 days.

The senators asked HHS and DHS for “weekly updates and briefings on your progress” until the reunifications are complete. They gave a deadline of July 6.

It was signed by Warren and Sens. Bill Nelson (Fla.), Bernie Sanders (I-Vt.), Robert P. Casey Jr. (Pa.), Kirsten Gillibrand (N.Y.), Richard Blumenthal (Conn.), Mazie Hirono (Hawaii), Edward J. Markey (Mass.), Cory Booker (N.J.), Tammy Duckworth (Ill.) and Tina Smith (Minn.).