The Justice Department is reportedly investigating Chinese electronics company Huawei over possible violations of sanctions against Iran, according to a report from The Wall Street Journal.

Details of the investigation are unclear, including what, specifically, the company is suspected of doing, but the probe is a new front in ongoing US scrutiny of Chinese manufacturers looking for a bigger slice of the American market.

Huawei has faced severe hurdles to operating in the US, as the government questions how cooperative the company might be with the Chinese government, and how that might affect national security. Earlier this year, AT&T pulled out of a major deal with the company, apparently after lawmakers raised concerns.

The cost of violating sanctions can be severely damaging. Last year, ZTE, another Chinese smartphone maker, was fined a record $1.2 billion for selling products to Iran and North Korea. Earlier this month, the Department of Commerce announced a ban on American exports to the company.

“Huawei complies with all applicable laws and regulations where it operates, including the applicable export control and sanction laws and regulations of the UN, US and EU,” a Huawei spokesperson said in a statement.

Update, 3:00 PM ET: Includes statement from Huawei spokesperson.