A bipartisan group of lawmakers intend to investigate the cause of the recent food poisoning outbreak that killed 25 people in a dozen different states.

House Energy and Commerce committee members wrote to the owners of Jensen Farms, asking them to brief committee staff and preserve documentation related to the outbreak that began on their Colorado farm in July of this year. Cantaloupes contaminated with listeria have killed 25 and sickened 123 so far.

The Food and Drug Administration reported this week that unclean equipment and unsanitary conditions at the packing plant likely caused the outbreak.

The committee also wants to hear from the FDA and the Centers for Disease Control and Prevention about how to prevent future outbreaks, the lawmakers said in a letter on Friday.

Recalls of listeria-contaminated processed meats and cheeses are common, but contamination of fresh produce is new.

Due to its long incubation period, people may not show symptoms for up to two months after consuming listeria-contaminated food. Symptoms include fever, muscle aches and diarrhea. People with weakened immune systems, such as the very young and very old, are most at risk for listeria. Most of the people sickened in this outbreak are over the age of 60, the CDC has reported.