AUSTIN, Texas — Tens of thousands of people streamed off university campuses in Texas and North Dakota after telephoned bomb threats on Friday.

Both campuses eventually were deemed safe and reopened by early afternoon, as authorities worked to determine whether the threats were related. A third evacuation order for much-smaller Hiram College in northeast Ohio was issued hours later and stayed in effect Friday evening.

The threats came as violent protests continued outside US embassies in the Mideast. Officials said the caller in the Texas threat claimed to belong to Al Qaeda, and a university spokesman said he had a Middle Eastern accent.

Also Friday, Valparaiso University in Indiana increased security and posted a warning to students after a vague graffiti threat was discovered. The school said the threat claimed ‘‘dangerous and criminal activity’’ would occur during the university’s daily chapel break. The FBI and local authorities searched the Indiana campus but found nothing suspicious.

The University of Texas received a call about 8:35 a.m. from a man claiming to be with Al Qaeda who said he had placed bombs all over the 50,000-student Austin campus, according to University of Texas spokeswoman Rhonda Weldon. He claimed the bombs would go off in 90 minutes. All buildings were evacuated at 9:50 a.m., Weldon said.

The deadline passed without incident, and the university reopened all buildings by noon.

Dean Bresciani, president of North Dakota State University, said 20,000 people also were evacuated from his school’s main and downtown campuses in Fargo after the school received its threat. FBI spokesman Kyle Loven said a call that included a ‘‘threat of an explosive device’’ came in about 9:45 a.m., but he declined to give further details.