Lawmakers are demanding answers to concerns about reports of Chinese cyber espionage regarding the IT company Super Micro.

Sens. Richard Blumenthal (D-Conn.) and Marco Rubio Marco Antonio RubioOvernight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers Democrats step up hardball tactics as Supreme Court fight heats up Press: Notorious RBG vs Notorious GOP MORE (R-Fla.) on Wednesday put pressure on the company, asking in a letter that it cooperate with law enforcement and explain more about the potential breach.

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The lawmakers’ concerns stem from a Bloomberg Businessweek report that detailed how the Chinese government was able to take advantage of vulnerabilities in Super Micro’s supply chain to install their own chips onto the company’s motherboards, which it then sold to many American firms including Apple and Amazon.

Super Micro, Apple and Amazon have all refuted the Bloomberg report, saying that their own investigations have not found evidence of a hack or of being compromised in the way described in the report.

Rubio and Blumenthal acknowledged the denials, but say that given the severity of the report, they still want further explanation.

“The nature of the claims raised alarms that must be comprehensively addressed,” the two wrote.

“We are alarmed about the dangers posed by backdoors, and take any claimed threat to the nation’s networks and supply chain seriously,” Rubio and Blumenthal continued. “These new allegations require thorough answers and urgent investigation for customers, law enforcement, and Congress.”

The two asked that Super Micro provide answers to several questions including if Super Micro has ever found evidence of hardware being tampered with, if it has investigated its supply chain as it previously committed to doing and if the Chinese government has ever requested access to Super Micro’s confidential security information.

Blumenthal and Rubio’s letter comes just after news that Senate Commerce, Science and Transportation Committee Chairman John Thune John Randolph ThuneOvernight Defense: Stopgap spending measure awaits Senate vote | Trump nominates former Nunes aide for intelligence community watchdog | Trump extends ban on racial discrimination training to contractors, military Remote work poses state tax challenges Senate GOP sees early Supreme Court vote as political booster shot MORE (R-S.D.) had previously sent letters to Apple, Amazon and Super Micro asking them for more answers as well and to brief committee staff on what they knew regarding Bloomberg’s report.