A hacking group connected to Iran has claimed responsibility for a cyberattack on a U.S. medical technology company, saying it was “retaliation” for a military strike on an elementary school in Iran that killed more than a hundred people.

Stryker, a Michigan-based company that produces medical equipment, said in a press release on Wednesday that it was “experiencing a global network disruption to our Microsoft environment as a result of a cyber attack.” On Thursday, the company said that there “is no indication of malware or ransomware” and that it believes that the attack was “contained to our internal Microsoft environment only.” 

“It is safe to communicate with Stryker employees and sales representatives by email and phone, and within your facility,” the company said.

“Our teams are working to understand the full impact to our internal environment,” Stryker said later on Thursday morning.

The company impacts more than 150 million patients in 61 countries each year, according to its website. CNN reported on Wednesday that U.S. agencies are investigating the incident to understand what, if any, effects the attack would have on patients.

Stryker didn’t identify the culprit responsible for the attack in its statement. But a hacking group, which calls itself Handala, appeared to take credit for the incident on social media. In a statement shared on X on Wednesday, the group said that the attack was done “in retaliation for the brutal attack on the Minab school.” 

A primary school in Minab, Iran, was struck by a missile on Feb. 28, killing about 175 people, more than 100 of whom were children, according to Iranian officials and teachers in the country. Video, satellite imagery, and expert analysis that have emerged in the wake of the incident suggest that it was the result of a U.S. air strike. The Pentagon has launched an investigation into the incident; the New York Times reported on Wednesday that the preliminary military inquiry found that the U.S. was responsible for the attack and that it was the result of a targeting error.

According to Handala’s X profile, the hacker group joined the social media platform this month. The Times reported that the group appeared to have emerged in 2023, several weeks after the conflict in Gaza started.

The attack on Stryker comes after U.S. intelligence experts cautioned that hackers with ties to Iran might launch cyberattacks against American companies and agencies, as the war in Iran continues.

The war, which began on Feb. 28 when the U.S. and Israel launched military strikes against Iran, has killed at least 1,270 people in Iran, according to state media outlets. Hundreds of people have died in the surrounding region as the conflict has spread in the Middle East. At least seven American service members have been killed since the war began.