She has flown to New Zealand with her son Rhodri and they have met up with Holland's girlfriend.
"We still hope that he will be found safe and well. The authorities are continuing their search. Others enquiries are ongoing. These could take several weeks, if not longer.
"We would just like to thank everyone for their messages of support at this heartbreaking time and to everyone who has contributed to the fund, it's been truly overwhelming."
Bay of Plenty District Health Board chief executive Pete Chandler. Photo / NZME
Bay of Plenty District Health Board chief executive Pete Chandler said his heart went out to Holland's family, his friends and colleagues during this "distressing time".
"David is a highly valued member of the hospital's theatre team, and he's a friend as well as a work colleague to many in the team.
"David is a junior anaesthetist with us at Tauranga Hospital, where he is completing his anaesthetist training, and the outpouring of concern for him is a mark of the affection in which he is held by everyone who knows him," he said.
"While the search goes on we've trying to support David's colleagues in the work environment as best we can as understandably many are deeply upset he is missing.
"I went to see our theatre team on Tuesday and all of them were talking about David and how valued and loved he is. We all expected that within a couple of days or so he would have been located, but of course, that has not been the case.
"Our thoughts and aroha are very much with David's family. His disappearance is just awful and our wellbeing team has been in touch with his family to offer our support.
"Staff members have taken part in the searches in and around the Pāpāmoa Beach area where David went missing, and we know this is a frustrating and upsetting time for all concerned as so many questions remain unanswered.
"As the search for David continues we pray for a positive outcome, and we are asking our staff members to look out for their work colleagues and to check in with them on how they're doing. Support is available for them if they need it."
Police believe Holland was last seen wearing a black jacket, striped T-shirt, long drawstring pants, size 11 shoes and carrying a black tote bag.
Hundreds of people have been involved in searches for his whereabouts.
He is originally from Wales and his mother and brother have travelled from Swansea to New Zealand to help search for their loved one.
On March 19 the Tauranga Police Search and Rescue team conducted a ground search for Holland concentrated on the sand dunes between Karewa Pde and Ocean Beach Rd.
The searchers included 148 volunteers but no relevant items were found, the police earlier said.
Rotorua Land Search & Rescue Mount Maunganui, Omanu and Pāpāmoa Surf Life Saving clubs, Tauranga Coastguard and Coastguard Air Patrol have also conducted searches.
Matt Shand, who became friends with Holland through playing ultimate frisbee in the past two years, described him as a "caring person" and a "lovely soul".
Shand said Holland was an "adventurous person", a keen cyclist and outdoorsman and was also known for going swimming alone.
He said the "hardest thing" was not knowing whether his friend was okay.
"We're all waiting for some news and hoping David will be found safe and well."
Shand urged anyone with any information about his whereabouts to contact the police.
A Go Fund Me page created to ease his family's financial worries during their time in New Zealand has raised more than $28,000.
Page creator Dean Ella wrote: "David is a wonderful person. His friends, family and colleagues love him for being kind-hearted, endlessly thoughtful and funny."
Ella also described him as active and outdoorsy and a keen cyclist, swimmer, hiker, ultimate frisbee player and an excellent swing dancer.
"It is due to this warm, open, adventurous personality that David has friends from all over the world and all walks of life that are looking for ways to help."
In a response to the Bay of Plenty Times' request for further details about the progress of the investigation, a police spokesperson said: "Police acknowledge the continued public interest in the investigation into the disappearance of Dr David Holland.
"The continued interest and offers of assistance from members of the public speaks to the high regard in which David is held in the community.
"Police will continue to explore any new information we receive about David's whereabouts, and we hope to be able to provide answers for David's family.
"At this time Police are not seeking volunteers to assist with further searches.
Police would "proactively release further information when it is available".
Anyone with any information that could help police locate David should call 105 and quote file number 220312/6869.
