An early morning Wednesday fire has closed a Northern California Planned Parenthood—the latest clinic attack in months of anti-abortion violence.

Dustin Bruley, a criminal investigator with the Stanislaus County District Attorney’s Office, said in an email to Rewire that the structure fire is “being investigated as a criminal matter” as arson, and authorities continue to review and analyze evidence. There were no reports of injuries.

Stanislaus Regional Fire Investigation Unit, Modesto Fire, and the Modesto Police Department responded at 3:30 a.m. to the Planned Parenthood facility in the Central Valley town of Modesto after reports of a fire, Bruley told Rewire.

Reports indicate the health-care facility will be closed for about a week. The extent of the damage is unclear, but local news outlets described shattered glass, a melted chair and a charred entrance.

A Planned Parenthood spokesperson told a local Fox affiliate that officials believe an incendiary device was thrown into the two-story building.

“The FBI is looking into it as we speak,” said Liz Figueroa, vice president of public affairs for San Jose-based Planned Parenthood Mar Monte.

“We’re constantly getting suspicious calls and things we’re monitoring,” Figueroa told the Modesto Bee. “We have noticed an increase in the past few months of suspicious calls and different packages left near the door that we don’t know what they are.”

Figueroa added that nothing thus far had seemed threatening. “We’re very cautious of everything,” she said.

A surge in clinic violence has followed the release last summer of a series of deceptively edited smear videos produced by an anti-choice front group aiming to take down Planned Parenthood.

Advocates suggest the incendiary rhetoric of the Center for Medical Progress (CMP) has fueled the spate of recent threats and attacks against abortion providers. The FBI has warned of “an uptick in attacks on reproductive health-care facilities” related to CMP’s ongoing smear campaign. A National Abortion Federation report released last month noted the upswing in violence, with 94 threats of violence reported in 2015, compared to one in 2014.

The string of attacks started in a health center in the Chicago suburb of Aurora on the morning of July 19, when a arsonist poured five gallons of gasoline around the front door and lit it on fire, causing an explosion.

Firefighters in New Orleans discovered in August that a car had been set alight at the construction site of a future Planned Parenthood facility, as the Guardian reported.

In September, a Pullman, Washington Planned Parenthood was firebombed by arsonists who threw a rock through a front window and then lobbed an explosive into the interior of the health center. Later that month, an arson fire ripped through a Thousand Oaks Planned Parenthood clinic in California. Authorities have arrested an Oxnard man in connection with the crime.

October saw a string of attacks, most notably at the Claremont Health Center in New Hampshire, a state the National Journal has referred to as “ground zero” in the legal and political battle to defund Planned Parenthood.

In November, a rampage by alleged gunman Robert Lewis Dear Jr. on a Colorado Planned Parenthood killed three people.

Days later, NARAL Pro-Choice America wrote to the U.S. Department of Justice, asking the agency to investigate clinic violence as domestic terrorism. Sen. Dianne Feinstein (D-CA) urged her fellow politicians to stop the “poisonous rhetoric” that was creating a climate of terror for “doctors, nurses and patients.”