The college in Leyland closed for 10 days last week after more than 30 students tested positive for coronavirus, with some cases identified as the Indian "variant of concern".
Runshaw principal Clare Russell said the decision to shut the college was made after discussions with Public Health England (PHE), who advised that a full closure would be the most effective way to break chains of transmission.
The public health specialists say the main reason they intervened in the outbreak was due to the presence of the Indian variant on campus, which has been confirmed through genetic testing and is thought to be more infectious.
‘How a car crash saved my life’: Royal Preston patient recalls chance cancer diagnosis as hospital’s major trauma centre marks tenth anniversary
North West paramedics get "first of its kind" training to better deal with emergency maternity calls
Preston great-grandmother who arrived in UK a penniless refugee gives £5k gift to renal unit at Royal Preston Hospital
‘No guarantees’ over Lancashire blood test hub as pathology collaboration boss announces retirement
Lancashire dental crisis: Fulwood dental surgery Dentistry by Cure Clinics is offering free checkups this month
The agency says is it continuing to provide "expert advice and support" to Runshaw following the outbreak and has urged all staff, students and their households to get tested to help limit the spread of the virus.
It has also said it will arrange for vaccinations for those staff who have yet to be offered the jab before the college reopens on May 17.
John Astbury, consultant in health protection at Public Health England North West, said: "Genetic testing has identified some cases of the Indian Variant of Concern and our health protection team has been working closely with the Leyland college and Lancashire County Council to provide public health advice and implement control measures aimed at helping stop the spread of the virus.
"This variant has been classified as a ‘variant of concern’ as evidence suggests it is more transmissible, however, there is currently no evidence that this variant causes more severe illness, increased risk of mortality or makes the current vaccines any less effective. Work is underway to understand that better.
"In Lancashire we’re working with the college, NHS Test and Trace and local authority public health teams on tailored intervention measures for variants.
"This includes increased testing in targeted areas, additional genomic sequencing of positive cases and enhanced contact tracing, which enables us to quickly identify any further cases and help prevent onward spread.
"As with any variant of the virus, it’s important to follow the basic measures of Hands, Face, Space, Fresh Air – wash our hands frequently, wear a face covering, keep our distance from others and get fresh air into enclosed spaces.
"All staff, students and their households have been advised to take a PCR COVID-19 test, to help reduce transmission and limit the spread of the virus."
Public Health England, Lancashire County Council and Runshaw College have declined to say how many students have contracted Covid-19, but sources say the number is "more than" 30.
On Monday (May 11), Balshaw's High School in Leyland - less than a mile away from Runshaw College - sent its Year 11 pupils home after reports of an outbreak of Covid-19 in the year group. The school has declined to comment.
It is thanks to our loyal readers that we can continue to provide the trusted news, analysis and insight that matters to you.
For unlimited access to our unrivalled local reporting, you can take out a subscription here and help support the work of our dedicated team of reporters.