"There does not appear to be oil flowing into the Gulf of Mexico," reported PBS based on its live feed of the spill. "Details of the new containment cap will be confirmed in the morning. The new containment cap has been placed & will be pressure tested."
"BP, of course, has to test the new cap over the well to make sure leak has officially stopped," CNN's Nick Valencia wrote. "The video looks hopeful."
While the oil spill was slowed by the new cap, and even seemed to stop for some time, oil could be seen leaking again in the oil spill live feed after 9 p.m. Eastern Time.
Tests will continue with the new cap and may last up to 48 hours, reports Yahoo's Brett Michael Dykes.
BP was quick to downplay the new cap's short-lived apparent success. "The sealing cap system never before has been deployed at these depths or under these conditions, and its efficiency and ability to contain the oil and gas cannot be assured," the oil giant said in a statement.
Successful or not, the cap is only meant to be a temporary fix, as The Telegraph notes. BP will continue drilling relief wells to try and provide a more permanent solution to the leak, and maintains that they are slated for completion in mid-August.