The JB Christie bakery in Airdrie was shut on Friday and Saturday while NHS Lanarkshire investigated nine confirmed and nine suspected cases.
Inquiries indicated a possible link to the bakery although all staff were found to be clear of the infection.
All the patients, who were treated as Monklands Hospital, were "well and responding to treatment".
NHS Lanarkshire said its investigation focused on iced cakes, decorated cakes and pastries produced at the bakery up to and including 27 April.
Since the closure the bakery has been subject to a "deep clean" and any fresh ingredients or foodstuffs disposed of.
Bakery owner Andrew Chisholm said: "Throughout this period of closure a team of environmental health officers were invited into the bakery to review all aspects, policies and working procedures and they were very satisfied with their findings and thanked us for our immediate reactions.
"The bakery employees have been very compliant with the requests from the health board to be fully screened and with almost immediate results stating that no employee was at any risk to the public to work within a food environment."
NHS Lanarkshire consultant Dr Josephine Pravinkumar praised the bakery for its co-operation.
She added: "Our initial investigations have indicated that there may be a link between these cases and the bakery.
"While the risk of contracting hepatitis A from products is very low, people who have consumed these products from the bakery since 1 March are being asked to look out for any flu-like illness, loss of appetite, nausea, fever, abdominal pains or jaundice (a yellowing of the eyes or skin).
"If anyone does experience any of these symptoms, they should contact NHS24 on 111 or their GP in the usual way."
A bakery in North Lanarkshire which closed following an outbreak of hepatitis A  will reopen on Tuesday.