A lane of First Avenue South in Seattle remains closed in the aftermath of Tuesday morning's sinkhole because a fill mixture failed to harden as fast as city agencies predicted.

Officials expected to have the Sodo site ready for traffic by Thursday evening, but the Seattle Department of Transportation (SDOT) announced late in the afternoon that road repairs were on hold while workers waited for fill material to set. The fill is a mix of fast-drying concrete and soils, poured into the hole.

Road crews were laying blacktop at the site just after 11 a.m. Thursday, in a northbound lane of First between South Massachusetts Street and Edgar Martinez Drive South. But the SDOT now says the fill beneath "has not set sufficiently to support traffic."

No estimate was given as to when crews can complete the road repair.

The sinkhole was caused by a break in a century-old, 16-inch-diameter water main.