(Adds fresh comment from police, Fraport, Lufthansa)
By Maria Sheahan and Ilona Wissenbach
FRANKFURT, Aug 31 (Reuters) - German police said a misunderstanding led to a security breach that prompted the evacuation of Frankfurt airport's Terminal 1 and caused delays and flight cancellations at Europe's fourth largest airport on Wednesday.
The alert was sparked when security staff at the terminal, a major hub for international travel and home to Lufthansa , requested police officers come over to check a suspicious female passenger.
Before the police could arrive, the passenger, who had two small children with her, had quickly left, a police spokesman said.
The passenger apparently thought the security check had finished and that's why she left, the spokesman said, declining to provide further details of what had raised the suspicions of security staff.
As a preventative measure, the police then took the decision to evacuate the entire departure area, which they later declared as secure, allowing operations to start again at 1030 GMT. All passengers were asked to go through the security check again.
The security breach interrupted flight operations, delaying departures and forcing some planes to divert to other German airports instead.
Airport operator Fraport said just over 100 flights were cancelled due to the evacuation.
Lufthansa was not immediately able to say how many of its flights were affected by the evacuation, but a spokesman said there could be isolated delays and cancellations on Thursday too as the carrier worked to get planes and crew back on schedule.
In a similar incident, a Spanish man was arrested at Cologne-Bonn airport in May after bypassing the security check, also leading to flight delays. (Additional reporting by Victoria Bryan and Hans Seidenstuecker; Editing by Richard Balmforth)