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Houston, Miami-Dade school districts receive threats

HOUSTON -- A day after school officials in Los Angeles cancelled all classes due to a threat that turned out to be a hoax, two more school districts said they received similar messages.

Houston Independent School District officials sent an automated voice message to parents on Wednesday night warning them of a threat "similar" to those received earlier this week in Los Angeles and New York, CBS affiliate KHOU reported.

"At this time, we do not believe the threat is credible, but as a precautionary measure, law enforcement officers are currently conducting random sweeps of school district buildings to ensure student safety," the recording said. "We have notified surrounding law enforcement agencies and will have additional officers on patrol in the morning."

Miami-Dade County Public Schools chief communications officer Daisy Gonzalez-Diego told CBS Miami that local, state and federal authorities deemed the threat "less than credible."

Gonzalez-Diego said "additional resources" would be on campus Thursday, but emphasized "It will be a regular school day."

On Tuesday, the Los Angeles Unified School District -- the second-largest in the country -- closed more than 900 public schools and 187 charter schools attended by 640,000 students after several school board members received an emailed threat warning of an attack similar to the deadly shooting in nearby San Bernardino two weeks ago.

Authorities in New York City said they received the same threat but quickly concluded that it was a hoax.