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President Donald Trump regularly makes news because of his tweets. Now a congressman is making news because of the device the president reportedly uses to tweet.

On Friday, Congressman Ted Lieu, a Democrat from Los Angeles, wrote a letter to the House Oversight Committee requesting an investigation into Trump's cybersecurity practices. In particular, he calls out Trump's apparent decision to keep using his personal Android phone instead of a secured phone the Secret Service issued him for his inauguration.

The letter is also signed by 14 other members of Congress and calls for a public hearing to discuss the issues.

"The device President Trump insists on using -- most likely the Samsung Galaxy S3 -- has particularly well documented vulnerabilities," the letter says. "The use of an unsecured phone risks the president of the United States being monitored by foreign or domestic adversaries, many of whom would be happy to hijack the president's prized Twitter account causing disastrous consequences for global security."

The White House didn't immediately respond to a request for comment.

Trump's alleged use of an unsecured phone comes after an election filled with hacks of the personal communications of Democratic political figures and organizations.

"Cybersecurity experts universally agree that an ordinary Android smartphone, which the president is reportedly using despite repeated warnings from the Secret Service, can be easily hacked," the letter continues.

This isn't the first time Democrats have raised concerns about Trump's phone. Last week, Sens. Tom Carper and Claire McCaskill sent a letter to Secretary of Defense James Mattis about whether the president is using a secure device to make calls and post tweets.