According to The Mirror, the cast noticed the noise after Anne Kirkbride stood up and started giving a speech in character as Blanche's daughter Deirdre for the ceremony.
Filming for the funeral has been taking place in recent weeks as a tribute to the character of Blanche, who was played by late actress Maggie Jones.
After hearing the snoring during shooting this week, it is thought that Weatherfield's regulars soon discovered that Malcolm Hebden, who plays busybody Norris Cole, was the source of the sound.
Kirkbride apparently then hugged her noisy co-star and said: "That's typical Maggie - she'll be looking down on us!"
A Coronation Street source said: "Anne laughed her head off. The snoring had been a mystery."
Blanche's send-off will air on the soap in May. In real life, Maggie Jones died in December following a period of ill health.