The College Board said students who mistakenly received low marks on their SAT exam would be notified by e-mail Thursday, after acknowledging that more students received incorrectly low scores than previously disclosed.

The board said Wednesday that 27,000 of 495,000 college entrance tests taken in October were not fully re-scanned for errors after scoring problems surfaced. When they were, an additional 375 students were found to have incorrectly low marks.

"We couldn't be more sorry for the total stress this has caused students and admissions officers and families," said Chiara Coletti, a spokeswoman for the College Board.

Coletti said admissions officers and school counselors were notified Wednesday.

"Some students will ask us to intervene" with admissions offices, Coletti said. "We'll do everything we can."

The latest problems came to light following a request that Pearson Educational Measurement, which scores most of the exams, confirm all 495,000 October tests had been rescored, Coletti said. That request followed an earlier oversight in which, a week after saying all the exams had been rescored, the College Board said it found 1,600 more exams that had been set aside for various reasons and had been overlooked. Of those, 18 students got incorrectly low scores, the College Board said Wednesday.

On Sunday, Pearson told the College Board 27,000 of the 495,000 tests had not been "completely processed" and would be rescored immediately, Coletti said. She said she could not provide further details on how the tests had been missed.

Douglas Kubach, chief executive of Pearson, said in a news release that the company is "determined to take every possible necessary step to restore confidence in this process," but a Pearson spokesman said he could not comment further on how the mistake happened.

The announcement brings to 4,411 the number of students who received incorrectly low scores. It is the latest in a string of embarrassing revelations for the College Board, the nonprofit organization that owns the exam, which said after discovering the 1,600 exams last week that it believed there would be no more problems.

"This would be a comedy of errors if the impact on human lives were not so tragic," said Robert Schaeffer of the group FairTest, which opposes excessive standardized testing. "How many more missing forms are there lost in the system? How many other errors have not been reported?"

The latest disclosure shows the need for an independent investigation, he said.

"There's clearly something wrong with the management at the College Board and Pearson," Schaeffer said.

The College Board said that from now on all answer sheets would be scanned twice, among other new precautions, and that it would retain consulting firm Booz Allen Hamilton to perform a comprehensive review within 90 days.

The initial discovery, disclosed to colleges beginning March 7, came as many schools were finalizing admissions decisions, prompting many to scramble to reconsider applicants whose scores were affected.

At least 600 students overall received incorrectly high scores on the exam, but those scores will not be lowered.