The Food and Drug Administration said it was investigating further to determine whether patients received bad blood.
"The blood supply is not as safe as it should be," said FDA Commissioner Mark McClellan. "I am troubled by apparent lapses in blood safety."
The Red Cross, which provides 45 percent of the nation's blood supply, said it is working hard to improve safety.
A year ago, the FDA went to court seeking contempt charges for 10 years of Red Cross safety violations. Friday's preliminary report on safety at the Red Cross biomedical headquarters suggests the problems have not been fixed, McClellan said, suggesting they point to "a culture willing to accept noncompliance."
Specifically, the FDA alleges that some Red Cross employees were instructed to skip required safety steps, and others altered records, to allow release of blood that had failed safety testing.
In addition, the Red Cross failed to screen out some people who were not supposed to give blood, the FDA said. It was unclear what happened to the units these people donated, the agency said.
More than 1,000 units of blood were unaccounted for, it said.
The FDA emphasized that anyone who needs a blood transfusion should get one, because the risk of forgoing a medical procedure is much higher than the risk of getting bad blood. The agency also noted that people who donate blood face no risk.
The Red Cross acknowledged problems and promised to fix them.
"The Red Cross understands more work needs to be done to further strengthen our processes and procedures, and we are fully committed to working collaboratively with the FDA to enhance our systems," Remesh Thadani, who heads biomedical services, said a statement Friday.
More than 200 individual violations were identified, the FDA said. Among them:
Lack of management control and quality assurance oversight. Required testing steps were not always documented, and some employees reported being told to skip required steps.
Data integrity: Employees were alleged to have changed records to indicate that flagged blood was safe.
Failure to correct deviations from previous inspections, including failure to follow standard operating procedures.
Release of unsuitable products. Donors in one Red Cross region who are found unsuitable are supposed to be listed in a donor deferral registry. They were not, and some went on to donate in other regions. In some cases, the FDA does not know what happened to their donated blood.
It was the first inspection of the Red Cross headquarters since last December, when the government asked a federal judge to hold the Red Cross in contempt for repeated violations of blood safety regulations, including shipment of contaminated blood.
In court, the FDA charged cited "persistent and serious violations" dating back 16 years and continuing despite a 1993 federal court order requiring improvements.
A year ago, the Red Cross vowed to fight the FDA. After getting a new director this summer, however, the two sides entered negotiations toward a settlement. The Red Cross said Friday it is making substantial progress; the FDA would not characterize the status of the talks.
The Red Cross refused to respond to specific allegations. But in a pre-emptive move, Red Cross officials had gathered reporters early this week to explain improvements made in recent months.
They said they have hired 175 people to work on quality and vowed better training for employees and improved computer systems that would be less prone to human error.
The Red Cross also has moved to an electronic blood donor record. In the past, some blood banks accepted blood from people who had not answered questions about the risk of HIV infection or who had answered "yes" to questions about high-risk behavior. Under the new system, people who leave these questions blank or answer "yes" will not be allowed to donate.
The Red Cross also displayed a chart demonstrating that the number of FDA violations had fallen over the past several years to about 100 in 2001. With Friday's inspection, more than 200 have been identified for 2002.