TORONTO (Reuters) - Some U.S.-bound flights from Toronto s main international airport were delayed on Wednesday afternoon due to an incident that prompted authorities to require some passengers to go through customs a second time, a spokeswoman said.  A customs breach  occurred shortly after 3:30 p.m. (2030 GMT) in Terminal 3, Toronto Pearson International Airport spokeswoman Beverly MacDonald said in an email.   Boarding was held while the situation was investigated and some passengers (had) to be reprocessed through U.S. Customs,  she said, adding that the breach was resolved around 5 p.m. (2200 GMT).  The breach occurred when passengers deplaning a flight from Calgary were inadvertently given access to a bypass door to the U.S. departures area, WestJet Airlines Ltd (WJA.TO) spokeswoman Lauren Stewart said in an email to Reuters. Terminal 3 serves flights to the United States on Alaska Air Group Inc (ALK.N), American Airlines Group Inc (AAL.O), Delta Air Lines Inc (DAL.N) and WestJet, according to the airport s website. 