The U.S.-led Coalition against Islamic State said Friday that it was investigating possible civilian casualties in Syria’s Middle Euphrates River Valley.

“Through self-reporting, Combined Joint Task Force-Operation Inherent Resolve is investigating a potential incident involving civilian casualties in the Middle Euphrates River Valley in Syria on Jan. 22, 2019,” the Coalition said in a statement.

There was no additional information about the incident, and the a spokesperson for the Coalition said CJTF-OIR could not discuss it while it was under investigation.

The monitoring group Airwars said Friday that it had tracked an event where a woman was killed and her two children injured on January 22 in Baghouz.

In its latest civilian casualty report released in December, the Coalition acknowledged that its operations in Iraq and Syria had killed or wounded at least 1,139 civilians since it began airstrikes in August 2014. Rights groups believe the death toll is much higher.

The Coalition and its partner forces on the ground are conducting clean-up operations against the last remnants of ISIS around the Middle Euphrates River Valley. Despite U.S. President Donald Trump’s announcement late last year that he would pull U.S. troops from Syria, airstrikes have continued in both Syria and Iraq.