Hundreds of viewers have lodged complaints after a Big Brother housemate was accused of bullying another contestant.
Watchdog Ofcom said it had received 361 complaints following Tuesday's broadcast, which saw Alexandra De-Gale verbally attack three fellow housemates.
Broadcaster Channel 4 is understood to have received a similar number of complaints itself.
An Ofcom spokesperson said 505 complaints had been received since the ninth series of the show began last Thursday and were all being looked into.
The watchdog has the power to launch an investigation if beaches of the broadcasting code are discovered.
The row centres on Alexandra, 23, criticising Rebecca Shiner for burning chips during cooking for a communal meal.
Rachel Rice stood up for the nursery nurse, but was attacked herself by Alexandra.
"You're getting on my f*****g nerves - I don't give a f*** what you think," the south Londoner said, before also criticising Stephanie McMichael when the teenager complained about her behaviour being abusive.
Big Brother followed up the row by warning Alexandra "bullying" was unacceptable in the house, although she is safe from eviction this week after four housemates failed the first week's task.
Last year in the celebrity version of the reality TV show, Bollywood actress Shilpa Shetty was the subject of alleged racial abuse from her fellow housemates, prompting almost 45,000 complaints from viewers.