Hours after a federal judge temporarily blocked enforcement of the most restrictive abortion law in the country, some Texas clinics have resumed providing abortions after a so-called fetal heartbeat is detected.

Under SB8, physicians are banned from providing abortions once they detect electrical activity within the cells in an embryo. That can be seen on an ultrasound as early as six weeks into a pregnancy — before many women even know they’re pregnant. Since the law went into effect on Sept. 1, clinics in the state have largely stopped providing abortions past that point, under the threat of potentially costly civil litigation.

After U.S. District Court Judge Robert Pitman granted the Biden administration’s emergency injunction to halt SB8 Wednesday night, Whole Woman’s Health, which operates four clinics throughout the state, said it resumed providing the abortions Thursday for an unspecified number of patients.

There is a 24-hour waiting period for most patients before they can get an abortion in Texas. Since Sept. 1, the clinics have been continuing the required consent process in the event an injunction was later handed down, allowing them to offer the procedure so soon after the injunction, according to Whole Woman’s Health founder Amy Hagstrom Miller.

“Last night, we reached out to some of the patients that we had on a waiting list to come in to have abortions today, folks whose pregnancies did have cardiac activity earlier in September,” Hagstrom Miller said during a press briefing with the Center for Reproductive Rights Thursday. “And we were able to see a few people as early as, 8, 9 this morning, right away when we opened the clinic.”

“And we are consenting people for care beyond that six-week limit today and hope that we will be able to take care of those people tomorrow and beyond as long as this injunction stands,” she added.

Texas promptly took steps to appeal the injunction to the Fifth Circuit Court of Appeals, Texas Attorney General Ken Paxton said late Wednesday. “The sanctity of human life is, and will always be, a top priority for me,” he said on Twitter.

Pending the outcome in that court, the case could make its way to the U.S. Supreme Court.

Legal experts and abortion rights advocates were unsure if physicians would feel comfortable providing abortions following the injunction, as there is the threat of being sued retroactively under the law, if it isn’t ultimately struck down.

The retroactive provision “remains a serious piece of concern for physicians and clinics” and makes for a “tenuous” situation in the state, Molly Duane, a senior staff attorney for the Center for Reproductive Rights, told reporters.

“But what we can say today is that there are independent providers across the state that are working to reopen full services and are doing so wary of the fact that the Fifth Circuit may take away this injunction at any moment,” she said.

Hagstrom Miller said there is “hope” but also “desperation” among patients at this time, as call volume has increased at the clinics. “Folks know that this opportunity could be short-lived,” she said.

In the wake of the injunction, Planned Parenthood’s Texas affiliates are “assessing what’s possible during this period of uncertainty,” their leaders said in a statement, while recommending that patients seeking an abortion call their local health center to discuss their options.

“This legal victory is an important first step toward restoring abortion access in Texas, but the fight is not over,” Planned Parenthood South Texas’ Jeffrey Hons, Planned Parenthood Gulf Coast’s Melaney Linton and Planned Parenthood of Greater Texas’ Ken Lambrecht said in a joint statement. “The state has already appealed this ruling and we don’t know if or when this injunction could be lifted, and the law could be back in effect.”

ABC News’ Nicholas Kerr contributed to this report.