Federal authorities investigating BP PLC's oil spill in the Gulf of Mexico are zeroing in on bad decisions, missed warnings and worker disagreements in the hours before the April 20 inferno aboard the Deepwater Horizon that spawned one of the worst environmental disasters in U.S. history.

In particular, the panel is examining why rig workers missed telltale signs that the well was close to an uncontrolled blowout, according to an internal document assembled by the investigators and reviewed by The Wall Street Journal. The document lists more than 20 "anomalies" in the well's behavior and the crew's response that particularly interest the investigators.

Investigators are also turning attention to decisions made by employees of Transocean Ltd., the rig's owner, in addition to those made by BP that day, the list indicates. In particular, the list suggests investigators are looking at whether better coordination between the two companies might have prevented the disaster. The document includes several instances of unexpected pressure increases triggering disagreements among workers from the two firms.

The anomalies list was prepared by a joint investigation of the U.S. Coast Guard and the agency that oversees deepwater drilling, the Bureau of Ocean Energy Management, Regulation and Enforcement (previously known as the Minerals Management Service). The panel will meet for five days of testimony this week and hear from BP and Transocean employees. The list reflects some of the main issues the panel intends to probe in that testimony.

Separately, on Sunday there was a report of oil seepage on the seabed near the damaged well. That could indicate BP's effort last week to cap the well might be forcing oil out through neighboring fissures in the rock.

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Thad Allen, the retired Coast Guard admiral heading the government response effort, wrote in a letter to BP that ships monitoring the area had found a seep an unspecified distance from the well. If leaks are confirmed, it could force BP to re-open valves on the cap, possibly allowing oil to flow more freely again.

A BP spokesman said the company is reviewing the letter and "continuing to work very closely with the government."

Continue reading at The Wall Street Journal