HOLLYWOOD HILLS (CBSLA) – Two people told police they were tied up during a home invasion in Hollywood Hills early Monday morning.

Police say one of the victims was hit in the head, possibly with a handgun, during the robbery on Oak Glen Drive around midnight.

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The victims, according to authorities, were finally able to call 911 four hours after being tied up in the home across the freeway from Universal City.

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All of the suspects, three men with guns, were able to escape before police arrived.

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An investigation is underway.