Ten direct COVID-19 cases have been linked to the Crossroads Hotel at Casula in Sydney's southwest and 11 close contacts have been identified as indirect cases after testing positive.

Thousands of people who visited the pub between July 3 and 10 have been told to get tested and self-isolate for 14 days.

AAP has spoken to multiple patrons who attended during the period of concern who said they were not asked to write down their contact details at any point during their visit.

All were "walk-ins", as people who made reservations gave their details at the time of booking.

"I was there on the Sunday night (July 5) about 5pm (and) there was no login. I walked straight in, ordered a meal, sat down and left," one patron said.

"It was like walking into a pub pre-COVID," another patron said.

Chelsea Sarkis said her details were taken when she made a reservation but she was surprised at the number of people at the venue on Saturday, July 4.

"The first thing we thought was there were 'way too many people here', we continued our night, took precautions, kept our distance," she told AAP.

Staff at the pub have rejected the claims, saying each table had pens and paper and management had drilled into them that they must ensure restrictions are followed and the 362-person capacity wasn't exceeded.

A bartender, who asked not to be identified as they were not authorised to talk to media, said police walked through the premises on July 3 and 4 without issue.

"(The) problem is some people didn't fill them out even when they were on the table and staff wouldn't find out until they left," the bartender told AAP.

"Some people refused and said they didn't want to due to privacy reasons, they were told to fill it out or leave and some people just filled out fake documents."

Jason Marlow, whose Marlow Hotel Management Group owns Crossroads Hotel, said the pub had "always followed the COVID-19 management plan including social distancing measures, staff training and a strict cleaning regime".

"More than 80 per cent of people coming to the hotel for food and beverage have already pre-booked using our booking app," he said in a statement to AAP.

"We have been following the health department's recommended one person per group booking rule, however, we are now changing our system to having licence scanning equipment at all (entry) points.

"There has never been a capacity breach at the venue."

NSW Chief Health Officer Kerry Chant said records kept by the pub were used for contact tracing.

The venue remains closed after shutting for a deep clean on July 10.

Australian Associated Press