With South Australia entering a lockdown from midnight on Thursday and ACT Health officials screening returning travellers, some parliamentarians opted to return early and not risk being blocked from the ACT.

Independent Senator Rex Patrick returned to South Australia on Sunday but on Monday morning received a phone call from the Senate president advising him to consider returning to Canberra due to the outbreak.

Senator Patrick said he returned to Canberra on Monday afternoon to eliminate the risk of not being able to attend the parliamentary sitting.

He said he understood all senators received the same phone call and knew of other parliamentarians who had similarly returned.

Trade Minister Simon Birmingham remained in South Australia on Wednesday afternoon and his office said no decision had been made about returning to Canberra.

Labor's Senate leader Penny Wong was in Adelaide on Wednesday and had also not reached a decision about returning pending health advice.

Greens senator Sarah Hanson-Young was already in Canberra for a parliamentary hearing and to ensure she would be able to attend the sitting period.

Senator Patrick said he believed it was a good decision to return as it meant he would not be excluded from the sitting period and he could more easily complete his work from his Canberra office rather than in locked-down South Australia.

The ACT has not shut its borders to South Australia and there is not yet an obligation to isolate unless travellers are unwell or get tested. However, non-essential travel between the ACT and South Australia is discouraged.